Islamist candidate Mohamed Morsy of the Muslim Brotherhood has been declared Egypt's new president, following a tense day of waiting for thousands of activists in Cairo's Tahrir Square.

Following a lengthy opening speech, the state election committee confirmed early polls, which suggested Mr Morsy had defeated former general Ahmed Shafik with 51.7 per cent of last weekend's run-off vote.

"What each candidate has received: Dr. Ahmed Mohamed Shafik Zaki, 12,347,380, 48.27 per cent. Dr. Mohamed Mohamad Morsy Isaa Al-Ayat, 13,230,000," the head of the Supreme Election Committee, Farouk Sultan, announced.

Morsy will succeed ousted president Hosni Mubarak, who was overthrown 16 months ago after a popular uprising.

He will, however, not inherit all of Mubarak's power. The military council which has ruled Egypt in the interim curbed the powers of the presidency earlier in the month, meaning the head of state will have to work closely with the army on a planned democratic constitution.

The 60-year-old Morsy won the first round ballot in May with a little under a quarter of the vote. He has pledged to form an inclusive government to appeal to the many Egyptians, including a large Christian minority, who are anxious about religious rule.